Specific brain regions such as the anterior cingulate gyrus, the left frontal lobe and the amygdala are now known to function abnormally at rest in depressed individuals. The current studies expand upon these resting findings by imaging depressed subjects and controls using O15 PET while they perform key neuropsycho logical tasks designed to activate and test the function of these regions. We have developed a facial emotion recognition paradigm, an emotional Stroop paradigm, and a sadness induc- tion paradigm in order to probe the neural networks involved in emotion recognition and emotion regulation. We have demonstrated that the left dorsolateral prefrontal lobe and the right anterior cingulate activate uniquely during facial emotion recognition. During the same task, depressed subjects activate this network differently. O15 Pet scanning, while neuropsychologically activating brain regions implicated in the pathophysiology of depression, is beginning to demonstrate the functional neuroanatomy of emotion recognition and emotion regulation.